Recently, in accordance with the increase in the amount of data, electric power consumption of data centers has dramatically increased, and power saving is required not only in servers which are primary IT (information technology) devices, it is also required in storage systems.
One of the power saving technologies of a storage system equipped with hard disk drives (hereinafter referred to as HDDs) is MAID (Massive Array of Inactive Disks). MAID is the technology where power saving is realized by spinning down or powering off an HDD or a plurality of HDDs which are not accessed. In this case, if the plurality of HDDs are divided into RAID (Redundant Array of Inexpensive Disks) groups, it is common to spin down or power off the HDDs that belong to the RAID groups.
Two types of methods of automatically executing MAID are interlocking the power saving control with the operation schedule and interlocking the power saving control with access from the host (host computer) such as a server. A typical example of the former method is interlocking the power saving control with the backup window; that is, spinning up the HDDs that configure the RAID group in which the backup data is stored at the start of a scheduled backup, and then spinning down the relevant HDDs at the end of the backup control.
Among the methods included in the latter type of interlocking with the host access, spinning down the HDDs that belong to the RAID groups if there is no access from the host over a certain length of time is well known (refer to Patent Document 1).
Furthermore, for periodical host access, the method of executing the HDD power saving control in accordance with the access cycle is suggested (refer to Patent Document 2).